Self-aligned void filling for mushroomed plating

ABSTRACT

A method of manufacturing includes 2 mushroom plating process starts with an overplated component which includes an enlarged mushroom head having outer portions which overhang a resist layer. The next step in the first process embodiment is a heating step in which the resist layer is hard baked. Thereafter, using a dry etch process, such as a reactive ion etch (RIE) process, the hard baked resist layer is removed in all areas except beneath the overhang of the mushroom head. The area beneath the overhang thereby remains filled with hard baked resist. Thereafter, the device is ultimately encapsulated such that no voids and/or redeposition problems exist under the overhang due to the presence of the hard baked resist. In an alternative process embodiment of the present invention the dry etch process is conducted first upon the resist layer, such that the resist layer is removed in all areas except under the overhang. Thereafter, the device is baked, such that hard baked resist remains beneath the overhang. Ultimately, the device is encapsulated and no voids or redeposition problems exist beneath the overhang due to the presence of the hard baked resist.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electroplating processesutilized in the manufacture of thin film devices, and more particularlyto mushroom plating process steps utilized in the manufacture of thinfilm devices such as magnetic read/write heads, as well as devicescreated using such process steps.

2. Description of the Prior Art

Electroplating process steps are utilized to create metallic structuresand electrical interconnects in the manufacturing of many types of thinfilm devices. Such thin film devices include integrated circuit devices,and thin film magnetic read/write heads utilized in hard disk drives,micro-electromechanical devices and the like.

As is well known, photolithographic techniques are utilized in theprocess steps that are utilized to create the electrochemically platedmetallic structures, and a significant limitation on the use ofphotolithographic techniques can occur where the hole or trench that iscreated is both deep and narrow, that is, it has a high aspect ratio. Insuch situations it is difficult to accurately create the trench or hole,and it is likewise difficult to effectively electrochemically plate intothe high aspect ratio trench. Prior art attempts to overcome theseproblems have utilized overplating techniques, also termed mushroomplating. These mushroom plating techniques may involve the utilizationof a shallower trench than is required for the desired height of themetal component structure, followed by the overplating of the trench,such that a generally mushroom shaped cap is formed in the area on topof the trench. The relatively shallow trench facilitates goodelectrochemical plating at the base of the trench, and the mushroomplating facilitates the formation of the tall component structure thatis desired. Likewise, in fabricating complex shaped metal structures,such as the yoke of the second magnetic pole of a thin film magneticwrite head, some portions of the photoresist trench may be significantlydeeper than other, shallower portions of the trench. In this situation,when the metallic plating is performed to a depth that fills the deeperportions of the trench, overplating occurs in the shallower trenchareas. With specific regard to such write head magnetic poles, typicallythe pole tip area is formed with a deep trench, whereas the wider yokearea is formed with a shallower trench. In the plating process, the poletip area is formed entirely within its deeper trench, whereasoverplating occurs in the yoke area, leading to the formation of amushroomed yoke.

In the prior art photolithographic plating techniques, following theplating step the photoresist is removed utilizing a wet etch chemicalremoval step. Significant problems are incurred at this point in theprior art mushroom plating processes. Specifically, where thephotoresist is chemically removed, an empty space is created beneath theoverhanging portions of the mushroom head. Thereafter, in followingprocess steps, unwanted redeposition of reactive species andparticulates can occur beneath the overhang, and it is difficult if notimpossible to remove the redeposited material beneath the overhang.Additionally, when the device is finally encapsulated at the end of themanufacturing process, voids are created beneath the overhang which aredetrimental to the performance of the manufactured devices. The processof the present invention eliminates the redeposition and void creationproblems previously incurred in employing mushroom plating techniques.

SUMMARY OF THE INVENTION

A first embodiment of the mushroom plating process of the presentinvention starts with an overplated component which includes an enlargedmushroom head having outer portions which overhang a resist layer. Thenext step in the first process embodiment is a heating step in which theresist layer is hard baked. Thereafter, using a dry etch process, suchas a reactive ion etch (RIE) process, the hard baked resist layer isremoved in all areas except beneath the overhang of the mushroom head.The area beneath the overhang thereby remains filled with hard bakedresist. Thereafter, the device is ultimately encapsulated such that novoids and/or redeposition problems exist under the overhang due to thepresence of the hard baked resist. In an alternative process embodimentof the present invention the dry etch process is conducted first uponthe resist layer, such that the resist layer is removed in all areasexcept under the overhang. Thereafter, the device is baked, such thathard baked resist remains beneath the overhang. Ultimately, the deviceis encapsulated and no voids or redeposition problems exist beneath theoverhang due to the presence of the hard baked resist. Devices that aremanufactured utilizing the processes of the present invention are alsoincluded within the invention. While not intended to be limiting in anymanner, one such device is a thin film magnetic head wherein the yokeportion of a magnetic pole is formed utilizing the mushroom platingtechniques of the present invention. Another mushroom plated componentfound in many devices is a mushroom plated electrical interconnectingstud that is formed utilizing the process steps of the presentinvention.

It is an advantage of the mushroom plating process of the presentinvention that mushroom plating can be conducted without incurringredeposition and void problems.

It is another advantage of the present invention that improved mushroomplated component can be obtained without significant additionalmanufacturing process steps.

It is a further advantage of the present invention that the space underthe mushroom head overhang is filled, such that redeposition does notoccur, and voids do not occur during encapsulation.

It is yet another advantage of the present invention that an improvedmushroomed yoke structure is provided for thin film magnetic writeheads.

It is yet a further advantage of the present invention that improvedmushroom plated electrical interconnect studs are provided for thin filmdevices.

These and other features and advantages of the present invention will bewell understood by those skilled in the art upon reading the followingdetailed description which makes reference to the several figures of thedrawing.

IN THE DRAWINGS

FIGS. 1-5 depict prior art process steps generally undertaken toaccomplish mushroom plating during the manufacturing of thin filmdevices;

FIGS. 6-10 depict process steps of a first embodiment of the presentinvention undertaken to perform mushroom plating during themanufacturing of thin film devices;

FIGS. 11-14 depict process steps of an alternative embodiment of thepresent invention undertaken to perform mushroom plating during themanufacturing of thin film devices;

FIGS. 15-17 depict prior art mushroom plating process steps generallyundertaken in the mushroom plating of the yoke portion of the secondpole of a thin film magnetic write head;

FIGS. 18-22 depict the mushroom plating process steps of the presentinvention as applied to the mushroom plated yoke depicted in FIGS.15-17, wherein FIG. 18 is a cross-sectional view of the device depictedin FIG. 17, taken along lines 18—18 of FIG. 17; and

FIG. 23 is a top plan view that generally depicts a hard disk driveincluding a magnetic head having a mushroom plated component of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-5 depict well known prior art mushroom plating technique processsteps, and a brief description thereof will serve as a basis forunderstanding the present invention and its advantages. FIG. 1 willserve as a starting point in the prior art process steps; it depicts afirst layer 14 upon which a plated component is to be formed. As is wellknown, a seed layer 18 is first deposited upon the layer 14 and aphotolithographic resist layer 22 is thereafter deposited upon the seedlayer 18. Utilizing photolithographic techniques a hole or trench 26 isformed through the resist layer 22 down to the seed layer 18. The basicstarting process configuration depicted in FIG. 1 is found and utilizedin many different device manufacturing processes whereverelectrochemical plating of a metal layer is being performed. Asdescribed in detail herebelow, some particular instances in which thebasic configuration depicted in FIG. 1 are utilized include the platingsteps involved in the formation of the yoke portion of a thin filmmagnetic write head, as well as the plating of metal studs that serve toelectrically interconnect the various components of thin film magneticheads with control circuitry and the like.

For various manufacturing reasons it is often desirable and/or necessaryto overplate into the hole 26, and as depicted in FIG. 2, whenoverplating is performed, the plated metal component 30 forms a neckportion 34 within the hole 26 and an enlarged outer portion 38 that istypically termed a mushroom head due to its shape. The next step instandard prior art photolithography is the removal of the photoresistutilizing a wet chemical etch process as depicted in FIG. 3. After thewet etch process has been completed, the mushroomed plated metalcomponent 30 remains, along with the seed layer 18. The component 30 isnow configured to include an exposed undersurface 40 disposed beneath anoverhanging portion 42 of the mushroom head 38, such that an open area43 exists under the overhanging portion 42.

Thereafter, the seed layer 18 is commonly removed in a broad beam ionetching process or similar dry etching process, in which the ion beam 44etches away the seed layer material 48, as depicted in FIG. 4. Sometimesetching needs to proceed further to remove the material under the seedlayer, to produce a notched P1 pole tip. A first significant prior artproblem occurs at this point in that the removed material 48 can becomere-deposited 50 upon the undersurface 40 of the overhanging portion 42.

A second problem with the prior art mushroom plating process occursduring the prior art encapsulation step, as is depicted in FIG. 5.Specifically, at some point during the prior art manufacturing processthe device components are ultimately encapsulated, typically using adieletric such as alumina, in a sputtering or other dry depositionprocess. When the encapsulation layer 56 is thus deposited, owing to theanisotropic, straight, line of sight directional nature of the drydeposition process, a void 60 can be formed in the area 43 beneath theoverhanging portion 42 of the mushroom head 38. Such voids 60 have beenshown to be detrimental to the performance of devices manufactured usingthese prior art manufacturing techniques. The present inventiontherefore provides improved manufacturing steps that eliminate theredeposition problem as well as the void problem, while retaining theoption for process engineers to utilize mushroom plating processtechniques where they are necessary or desired.

FIGS. 6-10 depict a series of process steps which comprise a firstmethod of the present invention for improved mushroom plating.Initially, FIG. 6 serves as the starting point of the first method ofthe present invention; FIG. 6 is identical to FIG. 2 and is provided forthe purpose of clarity of explanation. Therefore, as depicted in FIG. 6,a metal component 30 has been mushroom plated into a hole in a resistlayer 22 utilizing well known photolithographic and metal platingtechniques. Thereafter, as depicted in FIG. 7, prior to the removal ofthe photoresist layer 22, the device is hard baked to create a hardenedphotoresist layer 70. Significantly, in some devices the metal component30 must be annealed, such as is required in the manufacturing of thinfilm magnetic heads, where the component 30 is a magnetic pole and theannealing step is performed to enhance its electromagnetic flux flowcontrol properties. In that instance, the annealing step, which must beperformed during the manufacturing process, is advantageously performedwhile the photoresist layer 22 is present, and it results in the hardbaked photoresist layer 70. A typical annealing step utilizestemperatures of approximately 200 to 250° C. for approximately 1 to 5hours, which is comparable to the resist bake process parameters. Thus,the resist hard baking step does not necessarily result in an additionalmanufacturing step.

Thereafter, as depicted in FIG. 8, in a further departure from the priorart process steps, the hard baked photoresist layer 70 is removedutilizing a dry etch process such as a reactive etch process, preferablyan RIE process utilizing oxygen to create reactive species 74, and theresulting device is depicted in FIG. 9. Of course, other dry etchprocesses such as reactive ion beam etching (RIBE) and/or chemicallyassisted ion beam etching (CAIBE) can be utilized to remove the resistlayer 70, and references herebelow to an RIE process should be taken toinclude these and other dry etch processes that are suitable to removethe resist layer 70 as is described herein. As depicted in FIG. 9, owingto the straight, line of sight directional nature of the RIE process,portions 76 of the hard baked photoresist remain beneath theundersurface 40 of the overhanging portion 42 of the mushroom head 38.Additionally, the seed layer acts as a natural stop on the RIE etchingwith oxygen, because the oxygen reacts more strongly with the resistthan the metallic seed layer. Thus, relatively low RIE oxygen etchantenergies of approximately 50 to 100 eV can be used to effectively removethe resist. Significantly, in contrast to the prior art device depictedin FIG. 3, and described hereinabove, following the RIE etch step thereare no open areas 43 under the mushroom overhang 42. Thereafter, theprior art process steps depicted in FIGS. 4 and 5 involving the removalof the seed layer 18 and the formation of an encapsulation layer 56 ofthe component are completed. The process of the present invention thusresults in a mushroom component 78 such as is depicted in FIG. 10.Specifically, as is seen in FIG. 10, the remaining portion of the hardbaked photoresist 76 fully fill the area 43 under the mushroom head 38beneath the overhang 42. There is no redeposition problem because theopen area 43 beneath the overhang 42 formed in the prior art process isnon-existent, and voids 60 (see FIG. 5) which were a problem in theprior art process are also eliminated. The hard baked resist 76 is agood electrical insulator, and its presence presents no problems in thedevice 78. Thus the present invention constitutes an improved processfor manufacturing mushroom plated components that can be utilized tomanufacture many and various types of devices.

An alternative method of the present invention is depicted in FIGS. 11,12 and 13 as are next described. The alternative method starts with aphotolithographically mushroom plated component as depicted in FIG. 6and described hereabove. Thereafter, as depicted in FIG. 11, a dry etchprocess, such as RIE utilizing oxygen as the reactive species 80, isconducted. Following the RIE process step, as depicted in FIG. 12portions of the photoresist have been removed, whereas, owing to thedirectional nature of the RIE process, the portion 82 of the photoresistlayer 22 beneath the surface 40 of the mushroom overhang 42 remains.Thereafter, as depicted in FIG. 13, the device is heated to form hardbaked photoresist 84 beneath the mushroom overhang 42. As discussedhereabove, for certain devices which require an annealing step, theannealing step also serves as the step to hard bake the photoresist 22.Thus, as depicted in FIG. 3, the hard bake photoresist 84 entirely fillsthe area 43 beneath the mushroom overhang.

It is to be noted that the device as now constituted in FIG. 13 issubstantially identical to the device as constituted in FIG. 9 describedhereabove. Thereafter, the device depicted in FIG. 13 undergoes furtherprocess steps including the removal of outer portions of the seed layerand encapsulation 56, as depicted in FIG. 14 which is similar to FIG. 10described hereabove, to form a completed device. It can therefore now beunderstood that the significant difference between the process of thefirst embodiment depicted in FIGS. 6-10 and the process of thealternative embodiment depicted in FIGS. 11-13 is the reversal of thehard bake and RIE steps. Specifically, in the first process stepsembodiment the resist layer 22 is hard baked, followed by the RIE step.In the alternative process steps embodiment the RIE step is performedfirst and then followed by the hard bake step. While there may be subtledifferences in the resulting devices, the significant advantages of thetwo processes are identical; those being the elimination of theredeposition problem and the void problem that are found in the priorart mushroom plating manufacturing processes.

A specific application of the present invention in the plating of theyoke component of a write head pole portion of a thin film magnetic headis next described with the aid of FIGS. 15-22. Initially, as will beunderstood by those skilled in the art, FIG. 15 is a sidecross-sectional view of portions of a thin film magnetic write head 100during its manufacturing process. As depicted in FIG. 15, a P1 magneticpole 114 has been deposited, followed by a gap layer 116, insulatinglayers 122 and inductive coil members 124, and a further top insulatinglayer 126. Thereafter, a seed layer 128 has been deposited to facilitatethe electroplating of the yoke layer. Thereafter, as depicted in FIG.16, a photolithographic resist layer 134 is deposited upon the seedlayer 128; it corresponds to resist layer 22 of FIGS. 2 and 6.Typically, the resist layer 134 is deposited in a spin depositionprocess which tends to be planarized and which therefore results in arelatively thick resist layer portion 138 at the pole tip area 140, anda relatively thin resist layer portion 142 on top of the area 144 abovethe inductive coils area 124. Thereafter, utilizing photolithographictechniques the yoke shaped trench 146 is formed within the resist layer.It is significant to note at this point that the walls of the yoketrench 146 are thickest 152 (meaning the trench is deepest) at the P2pole tip area 140, and the trench walls are thinnest 156 in the area 144on top of the coils 124. In a typical application the thick walledportion 152 may be approximately 4 microns while the thinner portion 156may be approximately 2 microns.

As depicted in FIGS. 17 and 18 the next step in the manufacturingprocess is to electrochemically plate up the yoke 160 into the yoketrench 146, and mushroom plating occurs during this process.Specifically, the plating process is conducted to plate up the yoke 160in the P2 pole tip area 140 to fill the yoke trench 146 to almost itsfull depth. However, as noted above, the yoke trench walls 156 at thecoil area 144 are not as high as the walls 152 at the P2 pole tip area140. Thus, mushroom plating of the yoke 160 occurs in the coil area 144of the device to produce the mushroom head overhangs 164 depicted inFIG. 18, whereas no mushroom plating occurs in the deeper trench 152 atthe pole tip area 140.

Following the plating up of the yoke, an improved thin film head iscreated utilizing the process steps of the present invention.Specifically, rather than removing the photoresist layer 134 utilizing aprior art wet chemical etch process, which will result in the unwantedopen area under the overhang 164 as occurs in of the prior art (see FIG.4) and its resulting redeposition and void problems, the process of thepresent invention is employed. When utilizing the first embodiment ofthe present invention, as depicted in FIGS. 6-10 and describedhereinabove, the device 100 is next annealed (see FIG. 19), whichresults creating a hard baked photoresist 168. As is next depicted inFIG. 20 this step is followed by a reactive etch process such as an RIEstep using reactive species 172 to remove the hard baked photoresist 168in all areas except the area 178 under the mushroom overhang 164, asdepicted in FIG. 21. The device can then ultimately be encapsulated 182as shown in FIG. 22 without the problems of redeposition and voids underthe mushroom overhang. When utilizing the alternative process of thepresent invention, as depicted in FIGS. 11-14 and described hereinabove,after plating up the yoke 160, the RIE step using reactive species 172is first performed, followed by the annealing step which hard bakes theremaining photoresist 178 under the mushroom overhang 164. Thereafter,the device is ultimately encapsulated 182 and the redeposition and voidproblems of the prior art mushroomed overhang are likewise eliminated.

A simplified top plan view of a disk drive that includes a thin filmmagnetic head of the present invention is depicted in FIG. 23. The diskdrive 186 includes one or more hard disks 190 and one or more actuatorarms 194 that have a slider device 198 mounted thereto. A magnetic head100 of the present invention is formed on a surface of the slider memberutilizing the manufacturing techniques described hereabove. As is wellknown to those skilled in the art, the disk drive 186 includesadditional electromechanical and computerized components (not shown).

While the present invention has been shown and described with regard tocertain preferred embodiments, it is understood that those skilled inthe art will no doubt devise various alterations and modificationsthereto which nevertheless include the true spirit and scope of theinvention. It is therefore intended by the inventors that the followingclaims cover all such alterations and modifications that neverthelessinclude the true spirit and scope of the present invention.

What is claimed is:
 1. A method for overplating metallic components inthe manufacturing of thin film devices, comprising: depositing a resistlayer; forming an opening in said resist layer for the plating of acomponent therein; overplating said component into said opening, suchthat a mushroomed head is formed with overhang portions disposed aboveportions of said resist layer; heating said resist layer to form a hardbaked resist; and removing portions of said hard baked resist using adry etch process, such that portions of said hard baked resist remainunder said overhang portions of said mushroomed head.
 2. A method asdescribed in claim 1 wherein said dry etch process is a reactive etchprocess.
 3. A method as described in claim 2 wherein said reactive etchprocess is selected from the group consisting of RIE, RIBE and CAIBE. 4.A method as described in claim 2 wherein said reactive etch processutilizes oxygen reactive species.
 5. A method as described in claim 1wherein said thin film device is a thin film magnetic head.
 6. A methodas described in claim 5 wherein said metallic component is a yokeportion of a magnetic pole.
 7. A method as described in claim 6 whereinsaid heating step includes a magnetic pole annealing step.
 8. A methodas described in claim 1 wherein said component is an electricalinterconnecting stud.
 9. A method as described in claim 1 wherein anencapsulation step is performed following said dry etch process step.10. A method for overplating metallic components in the manufacturing ofthin film devices, comprising: depositing a resist layer; forming anopening in said resist layer for the plating of a component therein;overplating said component into said opening, such that a mushroomedhead is formed with overhang portions disposed above portions of saidresist layer; removing portions of said resist layer using a dry etchprocess, such that portions of said resist layer remain under saidoverhang portions of said mushroomed head; and heating said resist layerto form a hard baked resist.
 11. A method as described in claim 10wherein said dry etch process is a reactive etch process.
 12. A methodas described in claim 10 wherein said reactive etch process is selectedfrom the group consisting of RIE, RIBE and CAIBE.
 13. A method asdescribed in claim 11 wherein said reactive etch process utilizes oxygenreactive species.
 14. A method as described in claim 10 wherein saidthin film device is a thin film magnetic head.
 15. A method as describedin claim 14 wherein said metallic component is a yoke portion of amagnetic pole.
 16. A method as described in claim 15 wherein saidheating step includes a magnetic pole annealing step.
 17. A method asdescribed in claim 10 wherein said component is an electricalinterconnecting stud.
 18. A method as described in claim 10 wherein anencapsulation step is performed following said dry etch process step.